Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

There are no annotations, so behavioral transparency falls entirely on the description. 'Values discarded' is a useful trait and consistent with the schema's discard notes, but the description omits error behavior, whether nested keys are counted, and what is returned.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The definition is two short sentences with the action front-loaded and no filler. 'Values discarded' earns its place by clarifying an important behavioral detail.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no annotations and no output schema, the definition leaves critical gaps: all nine parameters are optional, none is identified as the JSON object to count, and the form of the result is not stated. An agent has to guess at the intended invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds no parameter-level detail, but schema descriptions cover all nine parameters, so the high-coverage baseline applies. The mapping is imperfect: the json parameter is described as text to validate, not as the object to count, though the parameter name makes it the most plausible input.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific action (count keys) and resource (a JSON object), so the core purpose is clear and distinct from validation or length-count siblings. It does not pinpoint which JSON object is meant or explicitly contrast with siblings such as validate-json, so it is not a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no guidance about when to call this tool, when not to call it, or which sibling tool would be a better fit. The only implied trigger is 'need a key count', and even then the description does not say what input to provide.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.